More Jetting Woes (Important!)

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I know that you guys have hashed and rehashed the jetting issue, but I have found very little info in the archives for my situation. I have a 2002 WR426 with the airbox/exhaust baffles removed and throttle stop cut. Everything else is totally stock. I live in Montana at about 5,000 feet and normal 60-80 degree temps. I want to rejet, but I'm a little afraid to. I really don't want to damage a bike I've worked two years to get! I'm not a newbie to the whole jetting deal, but I don't want to have this bike running lean. Everything seems to be okay as is; bike runs cleanly and I get only a very slight popping on really rapid deceleration. I think this can be fixed with the fuel mixture screw though. What would you guys suggest as a baseline? Keep in mind that I really want to baby this thing! I would rather compromise a little power than be running too lean. Thanks!

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If you want to get the most out of that bike the way you are set up you need to replace the stock WR needle with a YZ model. Try it one clip leaner than stock.

A little popping on decel is acceptable, but it may go away when you try the YZ needle.

I also think you should try a 40 pilot. At your altitude you don’t have much chance of ending up too lean. If you spend the $12 on the YZ needle you will be glad you did, if you buy this part number: (5JG-14916-E1) and run in the third clip you will probably be even happier.

IMO if you aren’t willing to try the YZ needle then you are better off leaving the jetting stock, with the exception of the smaller pilot, which should make it easier to start/harder to stall.

Hope this helps.

BTW I usually ride at 4k to 5k, and have great success with the PN I posted above in the WR/YZ 426 at clip # 3 with a 40 pilot, 160 main.

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I have a 2002 WR. I have the grey cut ,plug out. thottle cut. The bike runs spot on all the time. I think they got the jetting right in 2002. I can't find any reason to change it. I also feel the power is great with the WR timing. I run mostly tight woods, hill climbs. North East 0-1,000 ft. Get to try newly install scott dampner tommorrow.

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i have been told that these engines are best run on the lean side of things (good throttle response), and are more than happy to run this way. it is rare to damage it because of running too lean, and you would know if you are because performance will suffer greatly.